Question

Find the sum of all natural number less than 200 which are divisible by 7.​

Answer 1

Step-by-step explanation:

The required sum

=(1+2+3+...+199)−(3+6+9+...+198)−(5+10+15+...+195)+(15+30+45+...+195)

=

2

199

(1+199)−

2

66

(3+198)−

2

39

(5+195)+

2

13

(15+195)

=199×100−33×201−39×100+13×105=10732

Answer 2

Answer:

The required sum

=(1+2+3+...+199)−(3+6+9+...+198)−(5+10+15+...+195)+(15+30+45+...+195)

=

2

199

(1+199)−

2

66

(3+198)−

2

39

(5+195)+

2

13

(15+195)

=199×100−33×201−39×100+13×105=10732